1. Field of the Invention
The present invention relates to a portable recording apparatus for an electrocardiogram. More particularly it relates to a recording apparatus of electrocardiographic waves which has a display unit such as a liquid crystal display device for displaying recorded electrocardiographic waves such as Holter electrocardiograph.
2. Description of the Related Art
The inventors of the present application know an electrocardiogram recording apparatus capable of confirming the recording status and making diagnoses easily as irregular pulses by displaying the recorded electrocardiographic waves on a display device composed of liquid crystal.
In this apparatus, the electrocardiographic wave is sequentially displayed as a static waveform from left to right on the display screen. Once the wave reaches the right end of the display screen, a new wave is sequentially displayed by erasing the previous waveform, which has just been displayed. This method of displaying the waveform has been commonly used for monitoring the electrocardiogram.
Such a known apparatus as described above has disadvantages. For example, when three QRS groups (spikes corresponding to the start of a ventricular systole), indicating the time change of an electric potential with heart pulsations, are displayed from left to right on the display screen in order, the display position of the QRS group displayed on the leftmost end of the screen is not fixed, but is changed by displaying a new waveform thereon. As a result, it is difficult to visualize intervals between the R wave in a QRS group and the R wave in the next QRS group to be displayed to the right of the already generated QRS group, that is, it is difficult to visualize a change of R-R intervals (the change of a heart-beat rate). Furthermore it is difficult to capture the R-R interval between the R wave in the QRS group on the rightmost end of the display screen and the R wave in the next QRS group to be displayed on the leftmost end of the screen, since the display between the R-R interval will be interrupted.